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Your hands are capable of incredibly fine motor control, so much so that your limitation is actually your eyesight. Put a specimen under a good microscope and people can do very fine micromanipulations without much difficulty.

That's because synovial fluid has about 3 mg/mL of hyaluronic acid. Hyaluronic acid is extremely viscous and helps lubricate the surfaces between the cartilage and the synovium (a thin layer of tissue that lines the joint space).

I work as a medical laboratory scientist, and we get samples of synovial fluids all the time to do cell counts. A lot of the time, they're too viscous for our analyzer to sample, or they're too viscous for us to pipette into our hemocytometer. So we add hyaluronidase to break down the hyaluronic acid in the sample. It makes the goo disappear immediately. Then we can give the doctor an accurate white and red cell count.

Edit: On another note, I learned that a piece of infant foreskin the size of a postage stamp can produce approximately 4 acres of skin tissue in the laboratory. Due to that fact, they can be used as skin grafts for burn victims.

Internal forward models in brain. More and more evidence suggests that instead of the "normal" chain perception -> procession -> reaction - it would take too long - the brain basically hallucinate about the world, and sometimes corrects this hallucination according to the sensory information. But sometimes this correction fails, and then we have Anton–Babinski syndrome: the patient is physically blind, but fails to recognize it and continues the "see" the hallucination.

In more mundane situations, most people can relate: you hear something incomprehensible, ask to repeat, and then realize what was said before the counterpart repeats. Well, the brain predicted something incomprehensible, already reacted to this prediction, and only then the actual and more accurate processing of auditory information is done.

Duuuuuude! Finally, I fucking found out why that was! All these years of telling my dad that when he puts coriander in the soup it tastes like soap, and him reacting like I'm crazy or making shit up have come to a close! Thanks for that, made my day.

Ever wonder why splashing cold water on your face calms you down? It's because of this reflex. Basically, when cold water contacts your face, the brain activates a few very specific responses, designed to maximize your chances of surviving and not drowning. This reflex is strongest in aquatic mammals such as seals, otters, dolphins, etc. But humans have the response too, just weaker.

There are 3 reactions that happen in this order.

The first reaction that happens is your heart rate slows. This helps lessen oxygen in the bloodstream, leaving more for other organs.

The second reaction is some capillaries start to restrict. This happens specifically when under high pressure from deep diving. It starts with toes and fingers, moves to hands and feet, and eventually arms and legs. This leaves more oxygen to be used by your organs and the brain.

Lastly is a sort of water shift that occurs only during very deep dives. This is when your organs and circulatory walls open up and allow water and plasma to to pass freely throughout your thorax. This is so that your organs don't get crushed by the pressure. Even the alveoli in your lungs fill with plasma! It all gets reabsorbed when you leave the pressurized environment, so you don't, y'know, die.

Even when only your face is submerged in cold water, your body immediately starts to prioritize oxygen use to your brain and your heart. It's really neat!

One last note that I can't verify is true or not, is that when submerged your brain makes you very calm. This is in order to prevent excess oxygen use from freaking out. It would explain the calm feeling I feel when underwater for medium-long amounts of time, like when scuba diving. It would also explain why splashing cold water on your face is such a widespread thing!

Anyway, that's my most recent awesome human body fact. You have adaptations for you to survive when super deep underwater! I LOVE learning about this kind of thing.

People of Eskimo decent have a different adaption. When most people put their hands in ice cold water blood vessels constrict and blood is diverted to the core. Eskimo people are the opposite. Blood vessels open and flood the hands with blood. Helps prevent frost bite. Awesome shit. Evolution is still present.

Much more than just your nose! Your photosensitive cells are actually right at the back of the retina covered by several layers of epithelium and blood vessels which are all ignored as they are constant with respect to your retina.

You can observe them putting a small flashlight in the corner of your eye and trying to cast a ray that makes a very obtuse (almost a tangent) angle to your eye ball. If you jiggle the flashlight around, you will eventually catch a few angles where you can suddenly see all these blood vessels because their shadow falls in a different place than the eye is used to.

I work in an ER and I learned today that the Valsalva maneuver exists. Basically someone went into supraventricular tachycardia (SVT. Their heart's electrical system went into a crazy feedback loop and made it beat really fast) and my doctor goes in and says "hold your breath and act like you're taking a HUGE shit". Within 30 seconds her heart rate went back to normal. Blew my mind. I thought he was totally kidding. Turns out he had done a similar thing to a patient by putting a bag of ice on his testicles. Resolved the SVT. Bodies are fuckin weird.

Dude you just described exactly what I've been experiencing for over a decade now. My heart beats really hard and fast. I even posted something in /r/cardiology and I just got downvoted and ignored. I solve it the exact same way too. I went to a doctor and they didn't know what was wrong and basically said nothing was wrong. I'm definitely doing more research into what you called it. It makes so much sense. Thank you so much! It's such a relief to even potentially have a name to this problem I've had for so long.

Your inner eat senses that you're moving but your eyes don't see it. So the message that your brain receives is that you're hallucinating and you must have been poisoned so it tells your body to vomit out any poison.

I get motion sickness really really easily, compared to most people. If I have to go on a plane or boat, I have to take a crap ton of Dramamine, or i'd never make it 5 minutes. I'm fine in a car, as long as I'm looking out the window. The second I look anyplace BUT the window, I get sick. Do you know what makes some people more susceptible to getting sick?

I do some work on something called Umwelt Theory (https://en.wikipedia.org/wiki/Umwelt) as applied in film studies. it basically says: snails perceive time in 3 second snippets because of their neural system; birds see in UV and have a higher degree of color perception due to an extra cone in the eyes; owls have better vision in the dark than in the light, etc, etc. Every being's interpretation of the world is constructed only and entirely through the data received by our senses and our brain's interpretation of that. Therefore, each being sees and knows an entirely different world based on the capacities and limitations of their sensory apparatuses.

As I understand it, female embryos already have all of their eggs fully formed before the embryo's birth. These eggs can be removed before the birth of the embryo. If the embryo does not progress to a live birth, but the egg is fertilized (and implanted into a surrogate womb) and DOES result in a live birth, then that child is born with their biological mother NEVER HAVING BEEN BORN.

Even more disturbing, this could be repeated for rapid breeding to select for a trait. A mad scientist could create a new, highly specialized breed of human with this technique in a matter of decades, rather than centuries.

It's theorized that we were on our way to evolving poisonous bites. The cultures of bacteria in our mouths seem excessive for just digestion, like we're starting to deliberately formulate them to be dangerous to bite victims.

apparently the bacteria in a komodo dragons mouth is rather ordinary and isn't enough to kill prey. They do have anti-clotting agents in their venom though. So they just kill by savagely biting their prey and having them bleed out. We're talking about a ten foot beast of a lizard after all.

"Its now a test of endurance. Who will collapse first? The man or the animal? This was how men hunted before they had weapons, when a hunter had nothing more than his own physical endurance with which to gain his prize. Running on two feet is more efficient over long distance than running on four."

No matter how fast they run, no matter how far they run, no matter how hard they try to get away from the human the human will always eventually catch up. The human never tires. It will keep hunting its prey until the prey is dead.

The fear an animal would feel if being chased by a human.

I've seen part of that BBC document and eventually the animal just collapses onto the ground and watches as the human casually walks up to it and kills it.

Humans are basically the horror movie monsters of the animal world. Like a "Predator" type horror movie where the monster is this invincible technologically advanced beast that stalks its prey relentlessly, and sometimes keeps part of the carcass as a trophy.

Not only do we run on two legs for efficiency, we have no body hair and a liquid cooling system to radiate away all of the excess heat we generate while we're running down our terrified prey. We implement tracking skills that the animals we hunt wouldn't even be able to comprehend. We learn from them faster than they learn from us. We mimic their calls, set traps, and use weapons.

And that's just primitive hunting, not even touching on how drastically we alter the environments where we live today!

We're also the best throwers, and the best what I call ganger-uppers. Even stone - age people (of which there are a few groups even now) using whistles, signs, gestures, etc can gang up on anything and act as a super-creature against it. Wolves and so on gang up, but we're best at that too.

Exactly, we are horror movie monsters. The adaptability is the worse. Humans started out with pretty shitty equipment considering. Their teeth and claws (nails) suck. They had the endurance running as said.

Imagine being a animal. Suddenly, humans pop out of nowhere with heavy extended limbs (clubs) that can bludgeon you to death. Another day, they appear with some of the hardest claws in the jungle (stone dagger). These hunters keep adapting. Some time later, they have even longer limbs with claws that they can throw from a distance (spears). These monsters harness fire to keep themselves warm. And soon they wear the skin of their victims while they chase you. To end it all, they domesticated the wolves. These monsters took another dangerous animal and subjugated it to its will. And they are hungry...

edit: Wow, did not expect this comment to get so much attention. Thanks for the reddit gold!

And to make it worse, you can't go anywhere else either. Climb up a tree? So can they. Hide in a bush? They're one of the most perceptive creature on earth. Fly away? Prepare to get bombarded by spears and arrows.

Humans are the greatest predators on Earth, hands down. We're like the Batman of the animal kingdom. Given enough prep time, we could kill anything.

"As the human continues to flee, a growing despair washes over him. Although he may sprint, he may climb, and he may traverse several miles, the monopod will eventually outlast him. The efficient boing boing of the monopod haunts the human, until he simply collapses on the ground and waits to die."

There's a dude on Youtube that hunts with his bare hands, but always just catches the animal as a proof of concept and lets it go. He chased down a wild dog, caught a rabbit using poisonous snakes, and captured a vulture by lying motionless next to roadkill (only after covering himself in its entrails).

It's been a while since my mind has really been blown anew, but three things have always stuck with me.

1) People who have had a perinatal stroke (a stroke before being born) can lose an entire hemisphere (half a brain!). Functionality is almost identical to someone with a whole brain. Most of them have no idea and, if discovered, it's almost always in the context of a brain scan for something completely unrelated.

Which I've been told leads to very awkward conversations.

2) Most people's idea of how they control movements is that they start a movement, see how it's going, and adjust over and over very, very quickly - that when you reach for something, you manage to obtain precision by constantly correcting.

It turns out that this doesn't work. The time it takes to perceive information and program reactions is way too long.

Instead, you're just frighteningly good at predicting how to act so as to make corrections unnecessary. Consider the amount of precision involved in picking up a cup filled with water. Think of how many muscles are involved, how much their forces change. Now consider that you also know how the water will behave, how much it will weigh, just by looking at it.

3) All of that color you see? You're not actually seeing the vast majority of it with your eyes.

The central area of your vision (a surprisingly small area) sees color. Past that, you're relying almost entirely on brightness and your brain guessing colors (based on what it's seen before) and filling them in.

I remember an experiment we did in school, involving two identical sealed cans. Although we didn't know before the experiment, one can was empty and the other was filled with sand.

I can't remember the exact details of the experiment, whether the test subject picked up both cans at once or one at a time, but I do remember the result. Person picks up heavy can. Fine. But the empty can they end up accidentally shooting up over their head.

It's because the brain was expecting the empty can to weigh more and had sent what it thought was the appropriate signal to the muscles.

Opiorphin is located throughout the human body. Your spit actually has a very low amount of it. Your semen has 10x more than your spit. If anyone is thinking of saving up their spit as a painkiller ... don't, because you'll have more luck making a nice cum box.

I thought this was actually very interesting. I recently learned in my anatomy class about nerve endings and sensory receptors. In sensitive places, you have tons and tons of receptors.

For example, in the tip of your finger you have receptors that are a maximum of 1-3 mm but usually much less. That way, you can distinguish the feeling and know where it is actually coming from (as if you were poked somewhere on the finger).

However, in other places the sensory receptors are much bigger. On the back, for example, receptors can reach up to 6 cm. That means if someone were to lightly poke you with a two needles relatively close together, you wouldnt be able to feel that you were being poked with two needles since the same receptor would be obtaining sensory information and sending it to the brain at the same time.

How strong your body is. Our brains have a limiter that prevent our muscles from reaching their full power because we could hurt ourselves, in the same way cars have governors that keep you from revving too high or going too fast.

When we get a kick of adrenaline, that limiter can be removed. One story I like is the kid was working under his car (60s Impala, iirc) and the jack gave out, pinning him. Dude's middle aged mom comes out and is able to lift the car enough for the kid to get out.

My dad's a volunteer firefighter and says it's not uncommon for people to go to crazy lengths to saved loved ones. Walls torn down with bare hands to get to other rooms when there's fire in the halls, windshields punched out, etc. One time a guy showed up at a wreck his wife was in and pulled the door open with his hands, three firefighters couldn't get it open and were preparing to use the jaws of life. The frame was bent or something but he was able to bend the top of the door down where the window is.

Well, the muscles are already able to produce these insane strengths (I believe an often-quoted number is 3 times the normal, resting strength). It's the fact that the tendons and then bones aren't strong enough to handle it. Yeah, they're get a little tougher the more you moved your 'governor' up, but they have limits that your muscles wouldn't.

It's to save your tendons/bones from breaking more than your muscles from being damaged.

I always hear about such things, but I've never seen trustworthy sources or a video. You'd think with all the video cameras around today along with thousands of random accidents that there would be at least one recorded instance of super strength. Is this just an urban legend or is this actually verifiable?

Edit: Thanks for all the anecdotes instead of evidence. You are the cause of the problem.

“Consider the fact that for 3.8 billion years, a period of time older than the Earth's mountains and rivers and oceans, every one of your forebears on both sides has been attractive enough to find a mate, healthy enough to reproduce, and sufficiently blessed by fate and circumstances to live long enough to do so. Not one of your pertinent ancestors was squashed, devoured, drowned, starved, stranded, stuck fast, untimely wounded, or otherwise deflected from its life's quest of delivering a tiny charge of genetic material to the right partner at the right moment in order to perpetuate the only possible sequence of hereditary combinations that could result -- eventually, astoundingly, and all too briefly -- in you.”

A former neighbour of mine had actually cut himself working, and one of the tendons for his fingers was exposed just above his wrist. The doctors told him if he had severed it, they would have had to cut all the way up to his elbow to re-attach it.

The average human brain weighs 3lbs. Your personality traits, memories, emotional responses, nerve impulses, basic homeostatic mechanisms, and everything that tells your body how to work and react to stimuli is contained in three pounds. It's absolutely amazing that such a small organ can control everything that you are.

This happened to me while in 8th grade. I had a concussion from being hit in the head with a metal bucket full of solid concrete. from what I remember, I was much more talkative before the accident and could connect with people better, but I became much more loving and nicer towards the people who I could connect with afterwards. It's been hard, and getting in the old relationships I had with family members was hard, aggravating, and confusing. I couldn't understand why we didn't click like we used to anymore, and why they looked, talked with, and treated me differently than they had all of my life. This was especially prevalent with relatives I saw only once a year.

I do recall losing a few friends and exiting a few circles afterwards, and entering some other ones. The hardest part of that was re-learning people's names and what they were actually like. I remembered the faces, but the names and some to many personality traits were completely lost on me. I felt as if I had been taken from my old body and put in someone else's, while only being shown pictures of people beforehand. Being almost a total stranger to people who said they knew you and were your friends left me me feeling helpless, only until things started to come back. I got strange looks and was ridiculed when I asked longtime friends what their names were when they started talking to me or when I tried talking to them. The feeling of trying to belong again was just so weird.

I could do an AMA with my parents and I answering the questions if anyone really wants one.

From a mechanistic point of view it's different. You have chemicals in your body to make you sleep, and chemicals that make you more awake. Stimulants like cocaine or amphetamines act on receptors that make you more awake whereas caffeine prevents one of the chemicals in your body responsible for making you tired (adenosine to be more specific) from binding to its target receptor.

For years I had pain in my knee. My doctor would examine my knee and say it was fine. I finally requested an x-ray to find out why my knee hurt. The Dr. agreed, but said he also wanted to x-ray my hip. A year later I had a total hip replacement, and now my knee doesn't hurt anymore.

One of my biomechanics classes talked about stuff like this. Basically, your neck, hips, and ankles are stable joints, while your knees and mid-back are unstable. When there's a problem in the stable joints, it may not be noticeable there, but can affect the unstable joints. Cool stuff.

Quite a large part of how physically fit you remain is an epigenetic process. This means that it takes around 6 months to essentially reprogram your cells to a 'fit' metabolism, where certain protein synthesis channels are prioritised and adipose storage is reduced. This is one of the reasons why 'quick fix' diets can never work, a great deal of hard work is required to persuade the body to stay healthy.

Edit: People who keep telling me my statement is suspect without providing any evidence, please check my reply to Rhobes further down, it is a starting point of supporting sources that draws from publicly available sources.

While being exposed to open space is certainly not healthy to you by any stretch of the imagination, the time a human body can survive there is counted in minutes, not seconds as Hollywood movies will have you believe.

Yes, due to extreme decompression, you will lose all the air in your lungs almost instantaneously, causing a blackout within 5-15 seconds, all the liquids in your mucous membranes and eyes will first evaporate and then freeze instantaneously, exposed skin will be sun burnt within seconds, exposed blood vessels will begin to boil. But there is the one positive thing about the near-vacuum of space, and that is that there are very few atoms to transfer any residual body heat to, so the body will stay quite warm, even for hours. So in many cases, survival in the vacuum of space will come down to how much oxygen is remaining in the blood and being transfered to the vital organs, and that can last for several minutes.

People that lack certain receptors are possibility immune to HIV/AIDs. The CD4 receptors, CCR5 receptors, & the delta32 mutation are thought to be the biggest factor in HIV/AIDs immunity. The now defunct theory about missing CD4 receptors is that ancestors that survived the Black Plague had a "broken" RNA replication somewhere during transcription/translation process. (There are people better educated about these receptors than I & my info isn't exact so please don't take it as all out medical gospel.)

Also, Sickle Cell is a genetic mutation that combats Malaria. The little parasite can't find a comfy spot & just falls off of a Red Blood Cell effected by Sickle Cell. It's prevalent in Africa. In the Mediterranean there is a similar but completely different disorder called Thalassemia (sp?).

E. Coli is a wonder bacteria. You can play with its DNA/RNA coding & insert fluorescent jellyfish DNA/RNA into it & have glowing Petri Dishes. Some medications & immunizations are made using this fabulous little guy. They have flagellum & do a "run & tumble" movement to get around. They can also do a sort of handshake with each other & have "conversations" or sex this way. There are more of these little critters inside & outside the human body than there are people on Earth, past & presents. We are an e. coli planet.

The human intestinal tract is considered to be outside the body. When we form in utero, we start out as nothing more than a rectum. So from mouth to anus, it's just one long tube.

Apparently Cracked articles are pretty reliable. Their links always back up their claims. IIRC they HAVE to be strict about it, or else they'll get the reputation for making shit up, and that'd kill their site quickly.

Actually, they have nipples because they have the full system. It is in malfunctioning form for the reason you state, but for the average male... it could be used if one desired enough to get the system to run. As in, men are capable of producing breast milk.

I do remember hearing this a while ago. In high school my anatomy teacher said if a guy wanted to, they could take a pill (estrogen pill I think) and after taking it a while they could lactate. My friends and I all fantasized about how amazing it would be to have the power of milk right at the tips of our nipples.

LOL, yeah. Been there done that. Though I gotta admit it did feel weird. Like, hey, my chest is making food. What alchemy is this?

Of course, the baby is all: yes, it's the most amazingly wonderful thing ever to exist, feed it to me now. And an hour from now. And an hour after that. I can't tell 3 am from 3 pm, and neither can your tits.